Name: how motor units control muscle movement
Uploaded: 2025-10-23T11:49:15.000Z
Duration: 46 s
Channel: JoVE

- [Istruttrice] Un'unità
motore si riferisce

a un motoneurone

situato nel midollo spinale

e la popolazione di fibre
muscolari che innerva.

Mentre ogni fibra muscolare
scheletrica è innervata

da un solo motoneurone, gli
assoni da ogni motoneurone

possono diramarsi in una
serie di terminazioni

formando giunzioni neuromuscolari
in tutto il muscolo.

Come risultato, la stimolazione
di una singola unità motoria

provoca una debole contrazione
di tutto il muscolo.

A seconda del livello
di controllo necessario,

il numero di fibre per unità può variare

da pochi muscoli che
richiedono un movimento leggero

a diverse centinaia di
muscoli portanti meno precisi.

Stifani, Nicolas. "Motoneuroni e la generazione della diversità dei motoneuroni spinali." Frontiers in Cellular Neuroscience 8 (9 ottobre 2014). [<a href="https://doi.org/10.3389/fncel.2014.00293" target="__blank">Sorgente</a>]

unità motorie

Un'unità motoria è costituita da due componenti principali: un singolo neurone motorio efferente (cioè un neurone che porta gli impulsi lontano dal sistema nervoso centrale) e tutte le fibre muscolari che innerva. Il neurone motorio può innervare più fibre muscolari, che sono singole cellule, ma solo un neurone motorio innerva una singola fibra muscolare.

I neuroni motori inferiori sono neuroni efferenti che controllano il muscolo scheletrico, il tipo più abbondante di muscolo nel corpo. I corpi cellulari dei neuroni motori inferiori si trovano nel midollo spinale o nel tronco cerebrale. Quelli nel tronco encefalico trasmettono segnali nervosi attraverso il nervo cranico, e controllano principalmente i muscoli della testa e del collo. I neuroni motori inferiori provenienti dal midollo spinale inviano segnali lungo il nervo spinale e controllano principalmente i muscoli degli arti e del tronco del corpo.

Un neurone motorio inferiore attiva un potenziale d'azione che, in una sola volta, contraggono tutte le cellule muscolari scheletriche che il neurone innerva. Così, le unità motorie sono unità funzionali del muscolo scheletrico.

La dimensione di un'unità motoria, o il numero di fibre muscolari che il neurone motore inferiore innerva, varia a seconda delle dimensioni del muscolo e della velocità e precisione che il movimento richiede. I muscoli degli occhi e delle dita, che richiedono un controllo rapido e preciso, sono generalmente controllati da piccole unità motorie. In queste unità, i motoneuroni si connettono a un piccolo numero di fibre muscolari. Al contrario, le unità motorie per i movimenti degli arti e del tronco sono generalmente grandi e consistono in molte fibre muscolari.

Unità motorie

Un'unità motoria è costituita da due componenti principali: un singolo motoneurone efferente (cioè un neurone che trasporta gli impulsi lontano dal sistema nervoso centrale) ...

Education

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JoVE Core

Biology

Biologia

Human Biology

Biologia umana

Musculoskeletal System

Sistema muscoloscheletrico

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

Motor Units

how motor units control muscle movement

Motor units control skeletal muscle movement. A motor unit includes one efferent motor neuron, which carries signals away from the central nervous system, and all of the muscle fibers it innervates. A single motor neuron can connect with multiple muscle fibers, but each muscle fiber is innervated by only one motor neuron.

Lower motor neurons are the efferent neurons that control skeletal muscle, the most abundant type of muscle in the body. Their cell bodies are found in the spinal cord or brain stem. Neurons in the brain stem send signals through cranial nerves and mainly control muscles in the head and neck.

Lower motor neurons in the spinal cord send signals through spinal nerves. These neurons mainly control muscles in the limbs and body trunk. When a lower motor neuron fires an action potential, all of the skeletal muscle cells it innervates contract at the same time.

Motor units are the functional units of skeletal muscle. Their size depends on the size of the muscle and on how fast and precise the movement must be. Muscles in the eyes and fingers usually have small motor units for rapid, precise control, while motor units for limb and trunk movement are generally large and contain many muscle fibers.

How Motor Units Control Muscle Movement

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cross-bridge cycle

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motor units

Motor units control skeletal muscle movement. A motor unit includes one efferent motor neuron, which carries signals away from the central nervous system, and all of the muscle fibers it innervates. A single motor neuron can connect with multiple muscle fibers, but each muscle fiber is innervated by only one motor neuron. Lower motor neurons are the efferent neurons that control skeletal muscle, the most abundant type of muscle in the body. Their cell bodies are found in the spinal cord or...

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key terms and concepts

Learn how motor units link one motor neuron to many muscle fibers, and why small or large motor units help control precise or powerful movements.

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How Motor Units Control Muscle Movement

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